osx man page for sigmask

SIGSETMASK(2)						      BSD System Calls Manual						     SIGSETMASK(2)

NAME
     sigsetmask -- set current signal mask

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <signal.h>

     int
     sigsetmask(int mask);

     sigmask(signum);

DESCRIPTION
     This interface is made obsolete by: sigprocmask(2).

     Sigsetmask() sets the current signal mask.  Signals are blocked from delivery if the corresponding bit in mask is a 1; the macro sigmask() is
     provided to construct the mask for a given signum.

     The system quietly disallows SIGKILL or SIGSTOP to be blocked.

RETURN VALUES
     The previous set of masked signals is returned.

SEE ALSO
     kill(2), sigaction(2), sigblock(2), sigprocmask(2), sigsuspend(2), sigvec(2), sigsetops(3)

HISTORY
     The sigsetmask() function call appeared in 4.2BSD and has been deprecated.

BSD
								   June 2, 1993 							       BSD